Circulating fluidized bed reactor

ABSTRACT

A circulating fluidized bed reactor includes a filter apparatus for separation and recycling of fine particles which are entrained by the flue gas. The housing of the filter apparatus has a plurality of vertically disposed ceramic filtration tubes. The reactor chamber and filter housing are arranged back-to-back and have a common wall therebetween. A pre-separator for separation of coarse particles is provided which connects the reactor chamber with the filter apparatus. The reactor, the separator and the filter apparatus are encased in a pressure-proof cylindrical vessel. The walls of the reactor chamber and the filter housing can be water-cooled. In another form, the filter is comprised of a plurality of porous plates having ribs abutting adjacent plates to define passageways through the filter.

RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.72,597, filed July 13, 1987.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a circulating fluidized bed reactor inwhich solid particles are separated from the flue gas and recycled tothe reactor chamber. The invention may also be used in gasifiers.

In known circulating fluidized bed reactors, flue gas is removed fromthe upper end of the reactor chamber through a duct to a cycloneseparator. Entrained ash, unburned solid fuel, and other relativelycoarse particles, are separated from the hot flue gas and are returnedto the lower part of the reactor chamber. Before the flue gas isdischarged through a stack, it is passed through a dust collector ofsuitable design for removal of fine particles. Previously, theseparation and collection of dust particles have been achieved byvarious apparatus which have required substantial space and multipleflow lines interconnecting their various elements. Integrating thesevarious elements and functions into a substantially compact system hasnot heretofore been achieved.

In accordance with the present invention, there is provided a reactorhaving integrated therewith in a single vessel vertical filtration tubesfor separating solids from the solids-entrained gases. These tubes aremade of porous super alloys or ceramics, and which tubes are disposed ina filter housing located in back-to-back relation with the reactorchamber. The filtration tubes are used to clean the flue gas.

In certain applications, a pre-separator is located above the filterhousing in direct communication with the flue gas discharge outlet. Thepre-separator is thus located in back-to-back relation with the upperend of the reactor chamber. The pre-separator is used to separaterelatively coarse particles from the flue gas and return them to thereactor chamber before the gas enters the filtration tubes. The smallersized solid particles separate from the solids-entrained gas as the gaspasses through the porous tubes. Such solids remain within the tubesalong the inner walls thereof and are transported by the residual gasflow through the tubes for return to the reactor chamber. The structureand function of the filter apparatus which affords a thorough cleaningof the gas as it passes through the porous walls of the tubes aredescribed in U.S. Pat. No. 4,584,003, the disclosure of which isincorporated herein by reference.

Further, in accordance with the present invention, two different typesof pre-separators may be used in keeping with the compact nature of thereactor hereof. In a first type, the filtration tubes project above aninclined wall into an area in communication with the flue gas dischargeoutlet. The upper ends of the tubes are partially closed. In thismanner, the change of direction of the flue gas causes separation of thecoarse particles which are deposited on an inclined wall forming the topof the filter housing for conveyance back to the reactor chamber. Thegas with the smaller size solids flows into the filtration tubes andthrough a plurality of compartments formed in the housing. Eachcompartment is connected with a clean gas outlet for flow out of thevessel.

In another form hereof, the pre-separator may comprise a cycloneseparator disposed on top of the filter housing. An inlet duct is incommunication with the gas discharge outlet for tangentially introducinggas into the cyclone separator. An inner tube of the separator extendsupwardly into the cyclone and opens through an inclined wall into achamber in communication with the filtration tubes. The solids fall ontothe inclined wall for return to the reactor chamber, whereas the gasflows into the upwardly projecting tube for flow through and separationfrom the solids entrained therein by the filtration tubes.

From the foregoing, it will be appreciated that the reactor chamber andthe filter housing, together with the pre-separator on top of the filterhousing in certain applications, lie in back-to-back relation one to theother, thereby affording a compact unitary vessel. In this manner, thecombined and integrated reactor and filter housing may be enclosedwithin a pressurized vessel.

In another form of the present invention, a pair of filter housings maylie on opposite sides of the reactor chamber. Thus, each filter housinglies in back-to-back relation with the centralized reactor chamber. Eachmay have a pre-separator of either of the foregoing described type,depending upon the application. Each filter housing has outlet conduitsfor transporting the clean gas from the space between the filtrationtubes and the housing externally to the vessel. The solids which areseparated in any pre-separator fall by gravity along the inclined wallinto the central reactor chamber while the solids separated from thesolids-entrained gas in the filtration tubes flows toward the base ofthe reactor chamber for return thereto.

In a further form of the present invention, whether the reactor chamberand filter housing lie in back to back relation or the filter housingstraddles the reactor chamber, the coarse solids may be recirculatedthrough discrete pipes which form part of the filter assembly. Thecoarse solids exiting the discrete filter assembly pipes may berecombined with the finer dust particles flowing through the otherfilter pipes for combined flow into the combustion chamber.Alternatively, the coarse and fine solids may be introduced into thecombustion chamber separately.

In a preferred embodiment of the present invention, the reactor chamberand filter housing are enclosed in a pressure-proof vessel, preferablycylindrical. Also, the reactor is supplied with compressed air and thecleaned flue gas is used in a gas turbine. It will be furtherappreciated that the principles of the present invention can likewise beapplied to a gasifier rather than a fluidized bed reactor.

In certain fluidized bed reactor applications, solid particles mayadhere to the inner surface of the filtration tubes, tending to clog thetubes and inhibit the flow of gas through the tubes. While a pressurepulse may be provided in the gas outlet pipes to momentarily change thedirection of the gas flow through the porous tubes and thereby loosenthe particles adhering to the inner surfaces of the tubes, it has beenrecognized that such solid particles afford a beneficial scrubbingeffect on the tubes. Consequently, in certain applications, thescrubbing effect of the solid particles as they move through the tubestend to clean the tubes and keep the pores free of clogging material.Thus, in certain applications, a pre-separator may not be used and thelarger particles, separated in other applications by the pre-separator,are particularly directed for flow through the filtration tubes to scourthe inside of the tubes and maintain such surfaces clean. Moreparticularly, this is achieved by providing enlarged inlet openings tothe porous tubes such that additional quantities, particularly of thelarger materials, may flow through the tubes to clean the latter and forultimate return to the fluidized bed combustion chamber.

In a still further form of the present invention, the filter housing iscomprised of a plurality of porous plates. The plates may have ribsprojecting from one side thereof. When the plates are aligned generallyvertical one with the other, the free edges of the ribs engage the backside of the adjacent plate to form a plurality of passageways. Certainof the passageways communicate with the filter housing gas inlet at thetop of the filter such that gas may flow through the passageways andthrough the porous plates into other passageways formed by thejuxtaposition of the plates. These latter passageways are closed at boththe top and bottom of the filter housing and have communicating conduitsfor collecting the filtered clean gas flowing into such passageways forflow to a clean gas outlet. Alternatively, the filter housing may beformed of solid porous material having a plurality of bores formedtherein whereby gas flows into those bores in communication with the gasinlet at the top of the housing and through the porous filter housinginto those bores closed at the top and bottom of the housing for flow ofclean gas to the clean gas outlet.

In accordance with a specific preferred embodiment of the presentinvention, there is provided a circulating fluidized bed reactorcomprising means defining an upright reactor chamber having at least onegas discharge opening adjacent its upper end and at least one inletopening for solids separated from the gas adjacent its lower end. Thereis also provided a filter housing and means defining a plurality ofgenerally vertically extending horizontally spaced passageways, thesepassageway defining means in part formed of porous material and disposedin the housing. The housing and the reactor chamber are arranged inback-to-back relation one with the other. The housing has a gas inlet incommunication with the gas discharge opening and the passageways, asolids outlet in communication with the solids inlet opening, at leastone clean gas outlet, and means in the housing in communication with theone clean gas outlet for communicating gas flowing through the porousmaterial of the passageways with the one clean gas outlet.

In a preferred form of the invention for certain applications, the gasinlet includes means defining larger inlet openings for the passagewaysthan the internal diameter of the passageways to provide a solidsscrubbing action along the inside surfaces of the passageways tominimize clogging. Preferably, the inlet opening means are generallyfunnel-shaped elements, thereby increasing the quantity of solidsflowing through the passageways in comparison with the quantity ofsolids which would flow through the passageways if the inlet openingswere of the same diameter as the passageways. That is to say, the inletsfor each of the passageways have combined cross-sectional areas greaterthan the combined cross-sectional areas of the passageways to provideenhanced scrubbing of the solids along the interior surfaces of thepassageways.

In a further aspect of the present invention, there is provided a methodfor separating solids entrained in a gas from a fluidized bed reactorcomprising the steps of forming a filter comprised of a plurality ofspaced passageways of porous material, disposing the filter in ahousing, disposing the housing in back-to-back relation with thereaction chamber, flowing the gas with entrained solids through a gasdischarge opening in the reactor and into the passageways for flow ofthe gas through the porous material to clean the gas, collecting theclean gas flowed through the porous material and returning solidsseparated from the gas within the passageways to the reactor chamber.

Accordingly, it is a primary object of the present invention to providea novel and improved compact circulating fluidized bed reactor designwith separator, particularly a circulating fluidized bed reactor designwith separator suited for use in pressurized combustion or otherprocesses, as well as a method of operating the reactor.

These and further objects and advantages of the present invention willbecome more apparent upon reference to the following specification,appended claims and drawings.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a schematic vertical cross-sectional view of a circulatingfluidized bed reactor constructed in accordance with a preferredembodiment of the present invention;

FIG. 2 is a fragmentary enlarged cross-sectional view of a portion ofthe pre-separator forming a part of the reactor illustrated in FIG. 1;

FIG. 3 is a cross-sectional view of the reactor taken generally about online A--A in FIG. 1;

FIG. 4 is a view similar to FIG. 1, illustrating a further embodiment ofthe present invention;

FIG. 5 is a cross-sectional view thereof taken generally about on lineC--C in FIG. 4;

FIG. 6 is a view similar to FIG. 1, illustrating a still furtherembodiment of the present invention;

FIG. 7 is a cross-sectional view thereof taken generally about on lineD--D in FIG. 6;

FIG. 8 is a view similar to FIG. 1, illustrating still anotherembodiment of the present invention;

FIG. 9 is a cross-sectional view thereof taken generally about on lineE--E in FIG. 8;

FIG. 10 is a view similar to FIG. 1 illustrating still a furtherembodiment of the present invention;

FIG. 11 is a still further embodiment of the present invention;

FIG. 12 is a view similar to FIG. 1 illustrating another embodiment ofthe present invention; and

FIG. 13 is enlarged cross-sectional view thereof taken generally abouton line A--A in FIG. 12.

DETAILED DESCRIPTION OF THE DRAWING FIGURES

Reference will now be made in detail to the present and preferredembodiment of the invention, an example of which is illustrated in theaccompanying drawings.

Referring now to the drawing figures, particularly to FIG. 1, there isillustrated a circulating fluidized bed reactor 1. Reactor 1 comprises asubstantially vertical reactor chamber 2. The reactor chamber has afront wall 3 having a multi-sided angular shape, best illustrated inFIG. 3, and a planar rear wall. Front and rear walls 3 and 4,respectively, are water-cooled and are formed of vertically extendingtubes in a conventional manner. A filter housing 5 is disposed inback-to-back relation to reactor chamber 2. The rear wall 4 of thereactor thus forms a wall of the filter housing. A semi-circular wall 6having a multi-sided angular shape, similar to but reverse from wall 3,forms the remaining water-cooled wall of housing 5. Filter housing 5includes a wall or plate 8 which closes the upper end of the housing.Wall 8 is disposed below the top wall 9 of reactor 1 and is inclineddownwardly towards the reactor chamber. Wall 8 is provided with aplurality of openings and serves as a mounting plate for the upper endof a plurality of filtration tubes 10 defining gas passageways orchannels. As illustrated, tubes 10 are vertically disposed in housing 5.The lower end of housing 5 is provided with a generally funnel-shapedbottom part 11 having an outlet 12 through which solids are dischargedfrom housing 5. The lower end of filtration tubes 10 are connected to alower structural tube plate 16. Housing 5 is divided into a plurality ofsuperposed compartments by intermediate tube sheets 13, 14 and 15. Theupper ends of filtration tubes 10 protrude through the inclined plate 8and the openings of the tubes are covered by caps 17, as illustrated inFIG. 2, to avoid direct access of the solids into the tubes. Openings 33are formed in the sides of the upper ends of the tubes below caps 17 toenable entry of gas into the tubes and the tubes are therefore partiallyclosed at their upper ends.

Tubes 10 are formed of sintered ceramic material and are porous exceptfor the upper portion between the tube plates 8 and 13. The tubes atthat location are not permeable to gas. Compartment 18, 19 and 20between the tube sheets 13-16 are provided with gas outlets 21, 22 and23, respectively.

An inlet opening 24 for recycled solids is provided in the lower part ofthe reactor chamber. A standpipe 25 and a loop seal 26 connect theoutlet 12 in the bottom part of the filter housing with the solids inletopening 24 in the reactor chamber.

Air from a conduit 27 connected to an air plenum 28 below a grid 29supplies compressed air from an external source to the plenum. Feeders,shown schematically by the reference numerals 30 and 31, are adapted tofeed fuel, such as coal, and additives, such as limestone, into thereactor chamber above grid 29.

The flue gas with entrained solids leaves reactor chamber 2 through anopening 32 formed between its top wall 9 and the inclined upper tubeplate 8. The gas then flows into the passageways or channels defined byfiltration tubes 10. When flowing into tubes 10, the gas flows throughopenings 33 below cap 17, and abruptly changes direction, which causesseparation of the coarse fraction of the solids from the gas. Thesecoarse solids collect on the inclined tube plate 8, slide down along thesurface of the plate under the influence of gravity, and fall down intothe reaction chamber along the rear wall 4.

A portion of the flue gas, which after having entered the filtrationtubes for flow in a downward direction along the passageways or channelsdefined thereby, passes through the porous tube walls in the first gascompartment 18 while the solids remain along the inside of the tubes.

Another portion of the flue gas passes through the porous tube walls inthe second gas compartment 19. Remaining portions of the flue gas passthrough the porous tube walls in the third gas compartment 20. The gasin the space between the exterior of the tubes and the interior of thefilter housing compartments is removed through clear gas outlets 21, 22and 23 and transferred through a conduit 32 to a gas turbine, not shown.

The fine particles which are separated from the gas fall down or aremoved by the downward flow of the gas or coarser particles to the bottompart of the filter housing and are discharged through the solids outlet12. The solids are returned to reactor chamber 2 through standpipe 25and the loop seal 26. Particulate material which mainly consists of ashcan be removed from the loop seal or the lower end of the reactorchamber through conduits 34 and 35. The material removed is cooled in anash cooler 36.

The entire reactor chamber 2, filter apparatus 37, standpipe 25, loopseal 26 and the ash cooler 36 are encased by and within a pressure-proofvessel 7. The vessel is pressurized by the same air which is introducedinto the reactor chamber. As the inner and outer pressures acting onthese parts are equal, they do not have to be pressure-proof. Also, thewalls of the filter housing are formed of water wall tubes, therebyaffording a high heat resistance.

FIGS. 4 and 5 illustrate another embodiment of the invention which isgenerally similar in structure and operation to the embodiment shown inFIGS. 1 through 3. Only those structural and operational features whichserve to distinguish this embodiment from that shown in FIGS. 1 through3 will be described below. The same reference numerals have been used inFIGS. 4 and 5 to identify elements identical or substantially identicalto those depicted in FIGS. 1 through 3.

The embodiment of the invention shown in FIGS. 4 and 5 includes a filterhousing 5 and a reactor chamber 2 disposed in back-to-back relation onewith the other. The walls of the reactor chamber and the filter housingform a vessel having a cylindrical cross-section, as best illustrated inFIG. 5. Two parallel cyclone separators 40 are mounted on the filterhousing which operatively connect the reactor chamber with the filterapparatus 37. Each cyclone separator comprises a circumferential wall 41defining an annular separator chamber 42. A gas inlet duct 43 istangentially connected to each separator chamber. The inlet ducts 43 ofthe separators are connected to two discharge openings 44 formed in therear wall 4 of the reactor chamber for discharging gas from the reactorchamber. The upper end of separator chambers 42 are closed by top wall9. An inclined wall or plate 46 mounted on the filter housing forms thebottoms of the separator chambers. A central pipe 47 extends into eachseparator channel and is connected to the bottom. An opening 48 in thecircumferential wall of the separator chamber and rear wall 4 locatednear the bottom of the separators forms an outlet for separated solidmaterial. A plurality of parallel filtration tubes 10 defining gaspassageways or channels are disposed vertically in the filter housing.The ends of the tubes are connected to an upper tube sheet 13 formingstructural connections for supporting the tubes 10. Additionalintermediate tube sheets 14 and 15 divide the filter housing intocompartments. The top part of the filter housing below inclined wall orplate 46 forms an inlet chamber 49 which distributes the gas from thecyclone separator to the filtration tubes 10.

In operation, the flue gas with entrained solids is discharged throughthe reactor chamber gas discharge openings 44 at the upper end of thereactor chamber. A coarse fraction of the solids material is separatedat the periphery of the separator chamber and falls down to the bottomwall 46 of the chamber. The material collected on bottom wall 46 slidesdown its inclined surface under the influence of gravity and falls downinto the reactor chamber through the solids opening 48.

Gas, from which the coarse particles have been separated, is dischargedfrom the separation chambers 42 through gas outlet pipes 47 to inletchamber 49 of the filter apparatus which distributes the gas to thefiltration pipes. The gas flows through the porous filtration pipes forcollection external to the apparatus, with the smaller sized particlesbeing returned with a portion of the gas to the reaction chamber, aspreviously described in connection with the embodiment of FIGS. 1through 3.

Referring now to the embodiment of the invention hereof illustrated inFIGS. 6 and 7, which is generally similar in structure and operation tothe embodiments of FIGS. 1-3 and 4-5, only those structural andoperational features which serve to distinguish this embodiment from theother embodiments will be described below. Similar reference numeralsare used in FIGS. 6 and 7 as used in FIGS. 1-3 to identify identical orsubstantially identical elements.

In FIG. 6, the reactor chamber 2 is illustrated as a central chamber orcolumn which has a lower grid 29 to which feeders 30 and 31 feed coal orother fuels for burning in the chamber. Below grid 29, there is provideda plenum 28 and the upper portion of reactor chamber 2 is closed by awall 9.

In accordance with this embodiment of the present invention, disposed onopposite sides of the reactor chamber 2 are a pair of filtrationhousings 5, which are identical in construction and mirror-images of oneanother. Each filtration housing 5 has a plurality of upstandingfiltration tubes 10 supported at their upper ends by inclined wall orplate 8, the upper ends of which tubes 10 are closed by cap 17 in themanner illustrated in FIG. 2. The filtration housings 5 are separatedinto discrete superposed compartments 18, 19 and 20, separated by plates13, 14, 15 and 16. The space about the filtration tubes 10 and withinhousing 5 communicates with a clean gas outlet 21, 22 and 23. The lowerportions of the filtration housings 5 communicate with the reactorchamber through a bottom part 11 with outlet 12, which in turncommunicate with the chamber through the standpipe 25 and loop seal 26.

The operation of this form of the invention is similar to that describedwith respect to the previous embodiments. Importantly, the filtrationhousings are disposed in a straddling relation to the reactor chamber 2,with each filtration housing lying in back-to-back relation with thereactor chamber 2. In this manner, a compact housing is provided for theentirety of the apparatus.

Referring now to the embodiment of the invention hereof illustrated inFIGS. 8 and 9, which is generally similar in structure and operation tothe embodiments of FIGS. 1-3 and 4-5, only those structural andoperational features which serve to distinguish this embodiment from theother embodiments will be described below. Similar reference numeralsare used in FIGS. 8 and 9 as used in FIGS. 1-3 to identify identical orsubstantially identical elements.

In FIG. 8, the reactor chamber and filter housing 5 are arranged in backto back relation similar as the embodiments of FIGS. 1-3 and 4-5. Thecyclone separators 40 mounted on top of inclined wall 46 arestructurally and operationally similar to the cyclones of the embodimentof FIG. 4. In this embodiment, the inclined wall of plate 46 mounted onthe filter housing forms the bottoms of the separator chambers. Aplurality of parallel filtration tubes 10 defining gas passageways orchannels are disposed vertically in the filter housing similarly as inthe previous embodiment of FIGS. 4-5 except that a pair of enlargeddiameter or area tubes 100 formed of similar porous material as theremaining tubes 10 extend the full length of the housing. The upper endsof the tubes 10 and 100 are connected to an upper tube sheet 13 formingstructural connections for supporting the tubes 10. Additionalintermediate tube sheets 14 and 15 divide the filter housing intocompartments. The top part of the filter housing below inclined wall orplate 46 forms an inlet chamber 49 which distributes the gas from thecyclone separator to the filtration tubes 10. The upper ends of theenlarged area tubes 100 open through the inclined wall 46 to receive thecoarse solids sliding down wall 46. The lower ends of tubes 10 and 100exit into a common hopper 11 with an outlet 12 which, in turn,communicates with the chamber through standpipes 25 and loop seal 26.

In operation, the flue gas with entrained solids is discharged throughthe reactor chamber gas discharge openings 44 at the upper end of thereactor chamber. A coarse fraction of the solids material is separatedat the periphery of the separator chamber and falls down to the bottomwall 46 of the chamber. The material collected on inclined wall 46slides down its inclined surface under the influence of gravity into theupper open ends of filtration tubes 100.

Gas, from which the coarse particles have been separated, is dischargedfrom the separation chambers 42 through gas outlet pipes 47 to inletchamber 49 of the filter apparatus which distributes the gas to thefiltration pipes 10. The gas flows through the porous filtration pipes10 and 100 for collection external to the apparatus, with both thesmaller and larger sized particles being returned with a portion of thegas to the reaction chamber through the hopper 11, outlet 12, standpipe25 and loop seal 26. Alternatively, the coarse and fine solids can beintroduced into the combustion chamber separately.

It will be appreciated with respect to both the embodiments illustratedin FIGS. 4-5, 6-7 and 8-9 that the apparatus may be enclosed within apressure vessel similar to the vessel illustrated with respect to theembodiment of FIG. 1.

It will also be appreciated that the invention can be carried outwithout any pre-separator which separates the coarse fraction from thegas. Consequently, the pre-separators, whether they be cycloneseparators as in the embodiments of FIGS. 4-5 or the capped filtrationtube arrangement illustrated in the embodiment of FIGS. 1-3, may beeliminated and the coarse material may flow through the filtrationtubes, scouring the filtration surfaces, thus keeping the filtrationtubes clean.

For those applications where a pre-separator is not necessary ordesirable, and in keeping with a still further embodiment of the presentinvention, there is illustrated in FIG. 10 a fluidized bed reactorgenerally similar to the reactor illustrated in FIG. 1. In theembodiment hereof in FIG. 10, an enhanced scouring or scrubbing effectof the particles or solids as they flow downwardly through thefiltration tubes 110 is afforded by providing an inlet and tubeconstruction enabling a considerably larger quantity of particles toflow through the porous tubes. In this form, the reactor chamber 102 andfilter housing 105 are arranged in back-to-back relation similarly as inFIG. 1, separated by the wall 104. The filtration housing 105 includesan upper inclined wall or plate 108. Plate 108 is provided with aplurality of openings 133 and serves as a mounting plate for the upperend of the filtration tubes 110. The openings 133 which deliver thecombined gas and solids to the interior of the tubes 110 are generallyfunnel-shaped, with their larger openings at their upper ends. Thesmaller downward openings of the generally funnel-shaped openings 133fit the porous tubes 110. By this orientation and disposition offunnel-shaped openings, larger quantities of solid particles are enabledto flow into the tube and drywash or scrub the interior surfaces of thetubes to substantially minimize or eliminate clogging of the poroustubes by the particulate matter. Preferably, the larger openings at theupper ends of the funnels 133 lie flush with the inclined wall 108,although it will be appreciated that the enlarged funnel-shaped portionsof the tube inlets may project above the inclined wall 108. Suffice tosay, the generally funnel-shaped openings 133 increase thecross-sectional area extent for receiving the gas and solid particles ascompared with the combined cross-sectional area of the tubes atlocations downstream from the generally funnel-shaped inlet openings133. This increases flow velocity and the quantity of solid particlesflowing through the filtration tubes and hence the scouring or scrubbingaction of the particles along the interior surfaces of the tubes.

It will be appreciated from a review of FIG. 10 that plate 108 isinclined such that particles flowing by gravity therealong are returnedto the combustion chamber of the fluidized bed reactor 102. The plate108 could, of course, be horizontal or inclined in the oppositedirection in the event that it is desirable to flow all particles fromthe combustion chamber of the reactor into the filtration tubes.

As in the previous embodiments, gas outlets 121 and 122 lie incommunication with a chamber defined by the space or area between thefiltration tubes 110. Thus, a portion of the gas flowing through theporous tubes enters the chamber between the tubes for egress from thereactor via gas outlet passages 121 and 122. The solids flowing throughthe tubes flow into a funnel-shaped bottom part 111 for egress into astandpipe 125 and loop seal. As in the previous embodiments, theapparatus described is encased within a pressure-proof vessel.

Turning now to the embodiment hereof illustrated in FIG. 11, there isprovided a reactor chamber 202 in back-to-back relation with a filterhousing 205, separated by a common wall 204. In this application,pre-separation is achieved by centrifugal force as the gas is conveyedalong a curved path 232 between the upper reactor wall 209 and the upperplate 208 of the filter housing. In this form, the upper plate 208 isinclined downwardly in a direction away from the reactor 202 and towardthe side wall of the reactor in the flow direction of the gas. Thus, thecoarse, solid particles flow along the curved wall 232 for passage witha portion of the gas through a passageway 239 for return to thecombustion chamber of the reactor. Additionally, gas and solid particlesalso flow into and through funnel-shaped openings 233 formed in theinclined wall 208. The funnel-shaped openings 233 are arranged as in theprevious embodiment with respect to the inclined wall 208. Gas outletchambers 221 and 222 lie in communication with the chambers between thefiltration tubes 210.

Thus, in operation, the gas is initially pre-separated by flow along thecurved wall 232 such that the larger or coarser solid particles flowthrough the path 239 together with portions of the gas for return to thereactor 202. Another portion of the gas and particulate flow enters thefunnel-shaped openings 233 for flow into the porous filtration tubes210. As in the previous embodiment, gas flows along the passageways orchannels defined by the tubes and through the porous tubes into thechambers separated by plates 214 and 215 for flow through gas outlets221, 223 and 222. The particles flow along the interior surface of thefiltration tubes, effecting a washing, scouring or scrubbing action inthe course of their passage to maintain the pores of the porous tubessubstantially clean of clogging material. As in the prior embodiment,the solids flowing through the tubes 210 flow into a funnel-shaped area211 and through a standpipe and loop seal for return to the reactor.

The embodiment hereof illustrated in FIG. 11 is particularly suitablefor processes with substantial amounts of particles circulating, whereasthe embodiment of FIG. 10 is more suitable for processes with morelimited quantities of circulating particles.

Turning now to the embodiment illustrated in FIGS. 12 and 13, instead ofusing porous filtration tubes, the filter is formed of a series ofporous plates. In FIG. 12, there is illustrated the reactor chamber 302in back-to-back relation with the filter housing 305. As in the priorembodiments, the lower end of the filter housing 305 has a solidscollection chamber 311 and a standpipe 325 for feeding the solids backto the reaction chamber.

In this form, as illustrated in FIG. 13, the filter housing 305encompasses a series of substantially vertically extend plates 334 eachhaving laterally projecting ribs 337 projecting from one face of theplates. When the plates are juxtaposed vertically in lateral adjacentposition one to the other, it will be appreciated that the free edges ofthe ribs 337 engage the back side of the adjoining plate, i.e., engagethe side of the adjoining plate opposite its ribs 337. In this manner, aseries of horizontally spaced passageways or channels 335 and 336 areformed between the plates and ribs.

Preferably, alternating rows of the channels are open at their upperends, i.e., at 333 in FIG. 12, into the area of the gas inlet opening tothe filter housing 305. The lower ends of the passageways 335 are opento the solids collection chamber 311. The other passageways 336, whichalternate with passageways 335, are closed at both their top and bottom.Outlet conduits 321, however, communicate with each of the closedpassageways 336 for removing clean gas from the passageways 336 andcommunicating it to a clean gas outlet, not shown. The upper surfacedefining the inlet to the plates is inclined as in the previousembodiment such that larger particles may be pre-separated for flow backinto the reactor chamber 302.

In operation, the flue gas from the reaction chamber 302 flows throughthe gas inlet opening to the filter housing and particularly into thepassageways 335 open at the upper end of the filter housing. The gas andsolids separate by passage of the gas from passageways 335 through theporous vertical plates 334 into the passageways 336. The clean gas inpassageways 336 is removed by conduits 321 to the clean gas outlet. Theseparated solids in the passageways 335 continue to flow downwards tothe solids collection chamber 311 for return to the combustion chamber.

It will be appreciated that other forms of filter may be provided inkeeping with the present invention as illustrated in FIGS. 12 and 13.For example, porous plates spaced one from the other without ribs anddefining the passageways 335 and 336 alternately therebetween may beused instead. Also, porous plates with channels in the plates themselvesfor either the flue gas or the clean gas may be utilized. Blocks ofporous material, for example, may be used with boreholes formed in thematerial whereby gas would flow from the gas inlet through certain onesof the boreholes and through the porous material into certain of theother of the boreholes for removal from the filter.

It will be appreciated that objects of the present invention are fullyaccomplished in that there has been provided a circulating fluidized bedreactor which is compact in construction and capable of use within apressurized vessel.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. A circulating fluidized bed reactor,comprising:means defining an upright reactor chamber having at least onegas discharge opening adjacent its upper end and at least one inletopening for solids separated from the gas adjacent lower end; a filterhousing; means defining a plurality generally vertically extendinghorizontally spaced passageways, said passageway defining means partformed of porous material and disposed in said housing; said filterhousing and said reactor chamber being arranged in back-to-back one withthe other; said housing having a gas inlet in communication with saidgas discharge opening and said passageways, a solids outlet incommunication with said solids inlet opening, at least one clean gasoutlet; and means in said housing in communication with said one cleangas outlet for communicating gas flowing through the porous material ofsaid passageway defining means with said one clean gas outlet.
 2. Areactor according to claim 1 including separating means connecting saidgas discharge opening and said gas inlet for separating solids and gasesupstream of said housing
 3. A reactor according to claim 2 wherein saidseparating means comprises a wall inclined towards the reactor chamberfor returning separated solids to the reactor.
 4. A reactor according toclaim 2 wherein said separating means comprises at least one cycloneseparator having a separator chamber, said gas inlet including a duct incommunication the said gas discharge opening, a solids outlet in thelower part of said cyclone chamber in comunication with the reactorchamber and a gas outlet pipe extending into said cyclone chamber, saidcycle chamber having a bottom to which said gas outlet is connected. 5.A reactor according to claim 4 wherein said bottom is inclined towardsthe reactor chamber.
 6. A reactor according to claim 1 including astandpipe and a loop seal connecting said solids outlet and said solidsinlet opening.
 7. A reactor according to claim 1 wherein said gas inletincludes means defining larger inlet openings for said passageways thanthe internal diameter of said passageways to provide a solids scrubbingaction along the inside surfaces of said passageway defining means tominimize clogging.
 8. A reactor according to claim 7 wherein said inletopening means includes generally funnel-shaped elements thereby toincrease the quantity of solids flowing through said passageways incomparison with the quantity of solids which would flow through saidpassageways if the inlet openings were of the same diameter as saidpassageways.
 9. A reactor according to claim 7 including separatingmeans connecting said gas discharge opening and said gas inlet forseparating solids and gases upstream of said housing, said separatingmeans comprising a wall inclined towards the reactor chamber forreturning separated solids to the reactor, said passageway definingmeans extending through said wall with said larger inlet openingdefining means disposed above said wall.
 10. A reactor according toclaim 6 wherein the reactor chamber, the filter housing, the standpipeand the loop seal are encased in a pressurized vessel.
 11. A reactoraccording to claim 10 wherein said vessel is cylindrical.
 12. A reactoraccording to claim 1 wherein said passageway defining means comprising aplurality of discrete tubes.
 13. A reactor according to claim 1 whereinsaid passageway defining means comprises at least one porous platehaving a plurality of ribs extending from a surface thereof to define inpart said passageways.
 14. A reactor according to claim 1 wherein saidpassageway defining means comprises a plurality of porous plates eachhaving a plurality of ribs extending from a surface thereof define inpart said passageways.
 15. A reactor according to claim 14 wherein thefree edges of the ribs of a first plate thereof abut the side of asecond plate opposite its ribs whereby said first plate and the side ofsaid second plate define a plurality of passageways.
 16. A reactoraccording to claim 14 wherein said plates are aligned one with the otherin a generally vertical direction with the ribs of each plate projectinglaterally therefrom to abut the adjacent plate along a side thereofopposite its ribs to define a plurality of said passageways.
 17. Areactor according to claim 14 wherein said passageway defining means andsaid communicating means comprise a plurality of porous plates eachhaving a plurality of ribs extending from a surface thereof, said platesbeing aligned one with the other in a generally vertical direction withthe ribs of each plate projecting laterally therefrom to abut alaterally adjacent plate to define a plurality of generally verticallyextending channels, said communicating means comprising selected ones ofsaid channels, others of said channels comprising said passagewayswhereby gas flowing in said passageways flows through said porous platesinto said communicating channels for flow through said one clean gasoutlet.
 18. A reactor according to claim 1 including means for watercooling at least a portion of the walls of the reactor chamber and saidfilter housing.
 19. A reactor according to claim 1 including separatingmeans connecting said gas discharge opening and said gas inlet forseparating solids and gases upstream of said housing, said separatingmeans including a wall inclined towards the reactor chamber forreturning solids to the reactor, said passageway defining meansextending upwardly to project above said inclined wall, means forpartially closing end portions of said upwardly projecting passagewaydefining means for separating coarse solids from the gas for depositionon said inclined wall and return to said reactor and enabling gas havingsmaller sized solids entrained therein to flow into said passageway. 20.A reactor according to claim 1 wherein said filter housing is disposedon one side of said reactor chamber, said reactor chamber having asecond inlet opening for solids separated from the gas adjacent itslower end, a second filter housing, means defining a plurality ofgenerally vertically extending horizontally spaced passageways for saidsecond filter housing, said second passageway defining means in partformed of porous material and disposed in said second housing, saidsecond filter housing and said reaction chamber being arranged inback-to-back relation one with the other on the opposite side of saidreactor from said first filter housing, said second filter housing andsaid reactor chamber being arranged in relation in back-to-back relationone with the other, said second filter housing having a gas inlet incommunication with said gas discharge opening and said secondpassageways, a second solids outlet in communication with said secondsolids inlet opening, a second clean gas outlet, and means in saidsecond housing in communication the said second clean gas outlet forcommunicating gas flowing through the porous material of said secondpassageway defining means with said second clean gas outlet.
 21. Areactor according to claim 20 including a pair of separating meansconnecting said gas discharge opening and said gas inlets for said firstand second housings, respectively for separating solids and gasesupstream of said housings, each of said separating means including awall inclined towards the reactor chamber for returning solids to thereactor, said passageway defining means of each housing extendingupwardly to project above the inclined wall thereof, and means forpartially closing end portions of said upwardly projecting passagewaydefining means for separating coarse solids from the gas for depositionon said inclined walls and return to said reactor and enabling gashaving smaller sized solids entrained therein to flow into saidpassageways.
 22. A reactor according to claim 20 including a pair ofseparating means connecting said gas discharge opening and said gasinlets for said first and second housings, respectively, for separatingsolids and gases upstream of said housings, said separating means eachcomprising at least one cyclone separator having a separator chamber,said gas inlet including a duct in communication with said gas dischargeopening, a solids outlet in the lower part of said cyclone chamber incommunication with the reactor chamber and a gas outlet extending intosaid cyclone chamber, said cyclone chamber having a bottom to which saidgas outlet pipe is connected.
 23. Apparatus according to claim 1 whereinsaid passageway defining means includes a plurality of porous tubes,said communicating means includes a plurality of superposed compartmentsthrough which said filtration tubes extend, whereby said compartmentsreceive the gas flowing through said porous tubes and for communicatingthe gas to said one clean gas outlet.
 24. Apparatus according to claim 1including a pressure vessel, said reactor chamber and said filtrationhousing being disposed within said pressure vessel for operation at apressure other than atmospheric.
 25. Apparatus according to claim 1including separating means carried by said filter housing for separatingsolids into coarse and fine solids flow streams through said filterhousing, said separating means including at least one conduit having alarge cross-sectional area for receiving the coarse solids in comparisonwith said passageways which have a smaller cross-sectional area forreceiving the fine solids.
 26. Apparatus according to claim 25 whereinsaid conduit and passageways open at their downstream ends incommunication with said solids inlet.
 27. A circulating fluidized bedreactor, comprising:means defining an upright reactor chamber having atleast one gas discharge opening adjacent its upper end and at least oneinlet opening for solids separated from the gas adjacent its lower end;a housing a plurality of generally vertically extending horizontallyspaced filtration tubes in part formed of porous material and disposedin said housing; means defining a chamber about said tubes for receivinggas flowing through the porous material of said tubes; said filterhousing and said reactor chamber being arranged in back-to-back relationone with the other, said housing having a gas inlet in communicationwith said gas discharge opening for flowing gas and solids into saidtubes, a solids outlet in communication with said solids inlet openingand at least one clean gas outlet in communication with said chamberdefining means, whereby gas flows through the porous material of saidtubes into said chamber for communicating with said one clean gasoutlet.
 28. A reactor according to claim 27 including separating meansconnecting said gas discharge opening and said gas inlet for separatingsolids and gases upstream of said housing.
 29. A reactor according toclaim 27, including a pressure vessel, said reactor chamber and saidfiltration housing being disposed within said pressure vessel foroperation at a pressure other than atmospheric.
 30. A reactor accordingto claim 27 wherein said gas inlet includes means defining an enlargedopening for each of said tubes for providing a solids scrubbing actionalong the inside tube surfaces to minimize clogging of the filtrationtube pores.
 31. A reactor according to claim 27 wherein said gas inletincludes inlets for each said tube, the combined cross-sectional area ofthe tube inlets being greater than the combined cross-section areas ofthe tubes to provide enhanced scrubbing of the solids along the interiorsurfaces of said tubes.
 32. A method for separating solids entrained ina gas from a fluidized bed reactor comprising the steps of:forming afilter comprised of a plurality of spaced passageways defined by porousmaterial; disposing said filter in a housing; disposing said housing inback-to-back relation with said reaction chamber; flowing the gas withentrained solids through a gas discharge opening in the reactor and intothe passageways for flow of the gas through the porous material to cleanthe gas; collecting the clean gas flowed through the porous material;and returning solids separated from the gas within the passageways tosaid reactor chamber.
 33. A method according to claim 32 including thestep of separating the coarse solids from the solids entrained gas priorto flowing the gas into the passageways.
 34. A method according to claim33 wherein said reactor chamber and said housing are verticallyelongated and form part of a single vessel, and including the step ofreturning the solids to said reactor chamber includes flowing theseparated solids by gravity along a wall disposed adjacent the top ofsaid housing.
 35. A method according to claim 33 wherein the step ofseparating includes flowing the gas tangentially into a cycloneseparator.
 36. A method according to claim 35 wherein said reactorchamber and said housing are vertically elongated and form part of asingle vessel, wherein the step of returning the solids to said reactorchamber includes flowing the separated solids by gravity along a walldisposed adjacent the top of said housing and forming the bottom of thecyclone separator.
 37. A method according to claim 32 including the stepof enclosing said reactor chamber and said housing within a pressurevessel for operating said reactor at a pressure other than atmosphericpressure.
 38. A method according to claim 32 including the steps offlowing the coarse solids through at least one passageway of saidhousing and flowing the finer solids through the other passageways ofsaid housing.
 39. A method according to claim 38 wherein the step ofreturning the solids to the reactor chamber includes recombining thecoarse and fine solids after flow through the passageways for combinedreturn to the reaction chamber.
 40. A method according to claim 32including forming the inlets to the passageways to enhance the scrubbingeffect of the solids flowing through the passageways in comparison withflowing the solids through the passageways without such inlet formation.